Light sensitive photographic coating and method of manufacturing the same



Patented Apr. 21,1942

FICE

LIGHT- SENSITIVE PHOTOGRAPHIC COAT- ING AND METHOD OF MANUFACTURING THESAIVIE Rowland 8. Potter, Brightford Heights, and Ray Seward Hagaman,Irondequoit, N. Y., assignors to Defender Photo Supply 00., Inc.,Rochester. N. Y., a co poration of New York No Drawing.

This invention relates to a light sensitive photographic coating andmethod of manufacturing the same, and has for its purpose to afford alight sensitive coating having a variable steepness of gradation, orgamma, dependingupon the wave length or spectral region of the light towhich the coating is exposed, so that any desired gradation can be hadas the negative or character of the subject may require, by varying thecolor of the light, this application being Application January 14, 1941,Serial No. 374,368

18 Claims.

a continuation in part of application Serial No.

332,536, filed April 30, 1940, which application was a continuation inpart of application Serial No. 300,236, filed October 19, 1939.

More particularly the invention has for its purpose to produce such acoating by utilizing an emulsion that is sensitive to light of a givenwave length and characterized by a certain steepness of gradation, orgamma, when exposedto such light, and adding to said emulsion asensitizing dye which not only gives sensitivity to light of a differentspectral region than the region of natural sensitivity but when exposedto light of that region to which it has been made sensitive, it gives acharacteristic gamma or contrast differing greatly-usually softer--fromthe gamma of the natural region, so that by varying the light betweenthat to which the emulsion is' naturally sensitive and that to which thedye renders it sensitive, any gradation or contrast can be had.

Another object of the invention is to produce v gradation before dyeing,and accomplishing this by using a lesser quantity of the dye than wouldbe required to confer maximum sensitivity within the spectral regionaffected by the dye, or by using a' larger amount of the dye andrestricting its sensitizing action either by coating the emulsion on itssupport quickly after the dye is added, or by setting the emulsionrapidly and washing out a portion of the dye.

A further purpose of the invention is to afford a photographic lightsensitive coating that can be manufactured economically, and which withnormal developing and'fixing technique, is capable of producing. printsof widely varying contrast or steepness of gradation.

An emulsion can by this procedure be obtained that is'characterized .bya certain steepness of gradation, or gamma, when exposed to light of I acolor within the spectral region to which the emulsion is naturallysensitive, and a markedly softer gradation or contrast, varying from aslittle as to 50% or more, when exposed to light within the spectralregion to which the dye has made the emulsion sensitive. A paper. coated1:1-diethyl, thiopseudocyanine iodide.

with such an emulsion possesses a wide variation in gradation thatpermits it to be used commercially in place of several different papersthat have heretofore been required to give various degrees of gradationfrom soft to hard,

The invention may be carried out in different ways or by utilizingdifferent dyes, and according to a preferred method, the selected dye is,added to the emulsion in a restricted quantity,

substantially less than required to produce a maximum colorsensitization.

As an example of this procedure, a coating can be produced from 'anemulsion which naturally gives a high contrast or steep gradation,

by adding to one liter of such finished emulsion after washing from '7cc. to 11 cc. or approximately 9 cc. of a .05% solution in alcohol ofThe dye can be added either before or after washing-the emulsion, butpreferably after. The amount of dye thus used is considerably less thanwould be addedto produce maximum sensitivity, and

as a result, the emulsion possesses a considerably softer gradation whenexposed to light of a color within the spectral region to which the dyehas made-the emulsion sensitive than when exposed to light of a colorwithin the spectral region to which the emulsion is naturally sensitive.The amount of dye indicated above is substantially less than would berequired to produce maximum color sensitivity, and after adding the dye,the emulsion may be coated on the support as usual.

Another method of carrying out the invention resides in using a largerquantity of dye and restricting the length of time of action on theemulsion. One method of accomplishing this consists. ;in introducing thedye into the emulsion before setting and washing, While maintaining theemulsion at a relatively low temperature, and limiting the timeduring'which the dye is permitted to remain in the emulsion beforechil1- ing the latter.

For example, 300 cc. of a .05% solution of the dye may be added to 15liters of emulsion at approximately 86 F. The emulsion is permitted tostand for about two minutes, or other suitably short period of time, andcooled as rapidly as possible to a temperature of F., or lower, in aconventional chill room or. setting tank; The usual shredding, washing,and remelting operations of the emulsion are then carried out, afterwhich the emulsion can be digested at moderate temperatures or heated tocomparatively high temperatures without risk of destroying its variablegradation characteristics, the more so because a considerable amount'ofdye has been washed out. Following this, the paper or support is coatedin the usual manner.

In the procedure outlined, where 300 cc. of a .05% solution of dye isadded to 15 liters of emulsion, the emulsion preferably includes onepart silver bromide to about three parts gelatin and fifteen partswater, although .the emulsion may be otherwise composed as long .as thisapproximate relation between the amount of dye and silver halide ismaintained.

Any suitable dye which when used in restricted quantity will confer onthe emulsion a markedly different gamma, or gradation steepness in thesensitized region, or which is slow acting so as to enable restrictingthe dye sensitization by limiting the time' of action on the emulsion,may be successfully used to accomplish the stated results.

Among other dyes that are suitable and can be successfully employed arethe following:

(2 methyl-dihydrobenzthiazolylidene) -l 3'-ethylidenel -ethyl-oxindole)2 :2-diethyl-7 :7 -o -phenylene-thiacarbocyaninep-toluene sulphonate;

2:3 diethyl 5:6 benzthia-l :4 -quinazocyanine iodide;

2 l-diethyl-3 4-benzoxa-pseudocyanine iodide;

' l 1'-diethyl-thia-pseudocyanine iodide;

1:1 diethyl 9:9 ethylene 2:2 carbocyanine bromide;

thiacarbocyanine-p-toluene sulphonate; 2 :2'-diethyl-5 6-5 6 -dibenz-7:7'-ethylene-thiacarbocyanine-p-toluene sulphonate; 1:1'- diethyl-,3 3-3:3 -tetramethylindocarbocyanine iodide; 2' diethyl -4 5 4:5-tetramethyloxacarbocyanine iodide; 1' diethyl a. methyl seleno pseudocyanine iodide; 2' diethyl 8 methyl thia-carbocyanine bromide; 2'-diethyl-8-methyl-4: 4'-dichlor thiacarbocyanine chloride;

(1 :3 3 :5 tetramethyl-indolylidene) -2 :4 ethylidene- 1 -phenyl-3-methyl-pyrazole-5' -one) (1 :3:3: tri methyl indolylidene) 2:4ethylidene- 1 -m-tolyl-3 -methyl-pyrazole-5' -one) (-1 :3:3trimethyl-indolylidene) 2:4'-ethy1idene- (1 -phenyl-3-methyl-pyrazole-5'-one) (l 3:3 trimethyl indolylidene) 2:4-ethylidene- (1' p ethoxyphenyl3' methyl-pyrazole 5- one (1 3 :3 :5 tetramethyl indolylidene) -2 4'-ethylidene- 1 -phenyl-3 -methyl-pyrazole -5 -one) 1:3:3 trimethylindole 2:2 trimethine 6' methyl quinoline;

2:2 diethyl 5,-5 dimethyl oxacarbocyanine iodide; 2-:2 diethyl 5:5dimethoxy oxacarbocyanine iodide.

Another method of carrying out the invention by restricting thesensitizing action of the dye consists in adding the dye to the finishedwashed emulsion when the latter is ready for coating, and coating thepaper or other. support immediately. A dye such as described above, maybe emulsions, rendered color sensitive by means of certain sensitizerssuch as erythrosin, carbo; cyanine, isocyanine type dyes, frequentlyvaries according to the spectral region to which the emulsion isexposed, but the gradation conferred by such a dye is constant or of thesame degree,

irrespective of the amount of dye used.

Thus while the gradation conferred by the dye in such instance isdifferent from that of the 'regionand when exposed to the region of thenatural emulsion sensitivity, is slight and definitely insuflicient forany practical purposes in obtaining the necessary effects that haveheretofore required different papers of considerably varying contrastcharacteristics.

It is believed that the dyes disclosed herein have preferential actionon some of the silver halide particlesapparently,'the larger particlesbeing more rapidly and more completely sensitized than the smallerparticles. Hence, if action of the dye is restricted either by time, orquantityavailable in the emulsion bulk, then the particles of silverhalide distributed in the emulsion will be of varying color sensitivity.It is known that gradation is dependent on the relative sensitivity tolight of the different halide particles; so if the silver halideparticles are made widely variable in speed sensitivity, when exposed tolight to which the dye confers sensitivity, then softer gradation willobviouslybe obtained in the sensitized spectral region. It is thischaracteristic of the emulsion" that confers-a widely variable gradationand makes possible the use of one paper to obtain the various resultsthat previously required several papers. If the action of the dye is notrestricted, then all the silver halide particles will eventually beequally color sensitized, thus giving similar gradations whether exposedto light of the natural sensitivity region or to light of the region ofconferred spectral sensitivity.

With this method, the sensitizing action of the dye on the emulsion isless than if the dye were permitted to remain in the emulsion for alonger period before coating, and the sensitizing action of the dye isstopped by coating and drying the emulsion on the paper before maximumsensitization is reached, and at a point substantially less than suchmaximum.

With this procedure, the degree'of variation in the steepness ofgradation, or gamma, of the paper, between the spectral region of thedye and the spectral region to which the emulsion is naturallysensitive, depends upon the shortness of time between adding the dye tothe emulsion and coating the latter on the support, and best results arehad by completing the coating operation within approximately fiveminutes after the dye is added to the emulsion, during which theemulsion is maintained at the usual coating temperature.

While-the invention has been described with reference to certaindefinite methods, it is not confined to the particular steps,proportions, or dyes herein disclosed, and this application is intendedto cover such other dyes or methods as may come within the purposes ofthe improvement or the scope of the following claims.

6. The method of manufacturing a light sen- We claim:

1. The method'of manufacturing a light sen sitive photographic coatinghaving a widely variable gamma depending upon the spectral region of thecolor of the light to which it is exposed, which consists indistributing throughout 9. molten emulsion a sensitizing dye in aconsider-.

ably less quantity than required to produce maximum sensitivity,said'dye acting on the silver halide particles and possessing thecharacteristic of conferring a gradation which varies in the sensitizedregion with the amount of dye used and acting to impart to the emulsiona substantially softer gradation when exposed to light within thespectral region to which the dye has conferred sensitivity than whenexposed to light to which the emulsion is naturally sensitive.

2. The method of manufacturing a light sensitive photographic coatinghaving a widely variable gamma depending upon the spectral region of thecolor of the light to which itv is exposed, which consists indistributing throughout a molten emulsion a relatively small quantity ofa sensitizing dye which imparts to the emulsion a substantially softergradation when exposed to light within the spectral region to which thedye has conferred sensitivity than when exposed to light to which theemulsion is naturally sensitive, said dye acting on the silver halideparticles and possessing the characteristic of conferring a gradationwhich varies in the sensitized region with the amount of dye used.

3. The method of manufacturing a light sensitive photographic coatinghaving a widely variable gamma depending upon the spectral region of thecolor of the light to which it is exposed, which consists indistributing a dye having a slow sensitizing action throughout a moltenemulsion, limiting the time of action of the dye so as to produce lowercontrast in the sensitized region, and coating the paper or support withthe dye sensitized emulsion, said dye acting on the silver halideparticles and possessing the characteristic of conferring a gradationwhich varies in the sensitized region with the amount of dye used.

4. The method of manufacturing a light sensitive photographic coatinghaving a widely variable gamma depending upon the spectral region of thecolor of the light to which it is exposed, which consists indistributing a dye having a slow sensitizing action throughout a moltenemulsion at a temperature of approximately 86 F., said dye acting on thesilver halide particles and possessing the characteristic of confer-.ring a gradation which varies in the sensitized region with the amountof dyeused, permitting the emulsion to stand for approximately twominutes, cooling the emulsion as rapidly as possible to approximately 50F., thereafter shredding, washing, and remelting the emulsion, andcoating the support therewith.

5. The method of manufacturing alight sensitive photographic coatinghaving a widely variable gamma depending upon the spectral region of thecolor of the light to which it is exposed, which consists indistributing a dye having a slow sensitizing action throughout amoltenemulsion and immediately thereafter coating the support, said dye actingon the sliver halide particles and possessing the characteristic ofconferring a gradation which varies in the sensitized region with theamount of dye used.

sitive photographic coating having a widely variable gamma dependingupon the spectral region of vthe color of the light to which it isexposed, which consists in distributing a dye having a slow sensitizingaction throughout a molten emulsion, said dye acting on the silverhalide particles and possessing the characteristic of conferring agradation which varies in the sensitized region with the amount of dyeused; lowering the temperature of the emulsion and limiting the time andtemperature during which the dye is permitted to remain in the emulsionbefore chilling the latter, thereafter shredding, washing, and remeltingthe emulsion, and coating the support.

I. The method of manufacturing a light sensitive photographic coatinghaving a widely variable gamma depending upon the spectral region of thecolor of the light to which it is exposed,

, which consists in distributing a dye having a slow sensitizing actionthroughout a :rnolten of the color of the light to which it is exposed,

which consists in distributing throughout a molten emulsion asensitizing dye, said dye acting on the silver halide particles andpossessing the characteristic of conferringa gradation which varies inthe sensitized region with the amount of dye used, and restricting thesensitizing action of the dye on the emulsion to substantially less thanits maximum sensitizing action, whereby the emulsion has a substantiallysofter gradation when exposed to light within the spectral region towhich the dye has conferred sensitivity than when exposed to light towhich the emulsion is naturally sensitive.

- 9. The method of manufacturing a light sensitive photographic coatinghaving a widely variable gamma depending upon the spectral region of thecolor of the light to which it is exposed, which consists indistributing throughout a molten emulsion a dye having a slowsensitizing action, said dye acting on the silver halide particles andpossessing the characteristic of ,conferring a gradation which varies inthe sensitized region with the amount of dye used, and restricting thesensitizing action of the dye on the emulsion to substantially less thanits maximum sensitizing action, whereby the emulsion has a substantiallysofter gradation when exposed to light within the spectral region towhich the dye has conferred sensitivity than when exposed to light towhich the emulsion is naturally sensitive.

10. The product of the process of claim 1. 11. The product of theprocess of claim 2. 12. The product of the process of claim 3. 13. Theproduct of the process of claim 4. 14. The product of the process ofclaim 5. 15. The product of the process of claim 6. 16. The product ofthe process of claim 7. 17. The product of the process of claim 8. 18.The product of the process of claim 9'.

ROWLAND S. POTTER. RAY SEWARD HAGAMAN.

